Magnetic device including winding and insulators, and power conversion device using the same

ABSTRACT

A magnetic device includes a winding, and insulators by which the winding is surrounded. Each of the insulators is in contact with the winding. A gap exists between each two adjacent of the insulators in a winding direction of the winding.

BACKGROUND

1. Technical Field

The present disclosure relates to a magnetic device and a powerconversion device using the same.

2. Description of the Related Art

In recent years, power electronics has been attracting attention for thepurpose of overcoming environmental problems and energy problems. Powerconversion circuits often require high-voltage large-current operations.Consequently, securing the insulating property of transformers used inpower conversion circuits and heat-dissipation measures for windings andcores are required.

Japanese Patent No. 3481541 discloses a conventional transformer inwhich a primary winding and a secondary winding are woundconcentrically, and the windings are molded with a thermosettinginsulating resin having high thermal conductivity.

SUMMARY

A magnetic device according to an aspect of the present disclosureincludes a winding, and insulators by which the winding is surrounded,each of the insulators being in contact with the winding, a gap existingbetween each two adjacent of the insulators in a winding direction ofthe winding.

Additional benefits and advantages of the disclosed embodiments willbecome apparent from the specification and drawings. The benefits and/oradvantages may be individually obtained by the various embodiments andfeatures of the specification and drawings, which need not all beprovided in order to obtain one or more of such benefits and/oradvantages.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view depicting an example of the structure of atransformer according to embodiment 1;

FIG. 2 is a cross-sectional view along a plane that includes the windingaxis of the transformer according to embodiment 1;

FIG. 3 is an exploded perspective view of the transformer according toembodiment 1;

FIG. 4 is a cross-sectional view along a plane perpendicular to thewinding axis direction of the transformer according to embodiment 1;

FIG. 5 is a drawing depicting an example of heat distribution in a crosssection along a plane that includes the winding axis of a transformeraccording to a comparative example;

FIG. 6 is a drawing depicting an example of heat distribution in a crosssection along a plane that includes the winding axis of the transformeraccording to embodiment 1;

FIG. 7 is a cross-sectional view along an XY plane depicting an exampleof the shape of an end of an outer bobbin;

FIG. 8 is a cross-sectional view along the XY plane depicting an exampleof the shape of the end of the outer bobbin;

FIG. 9 is a cross-sectional view along the XY plane depicting an exampleof the shape of the end of the outer bobbin;

FIG. 10 is a cross-sectional view along the XY plane depicting anexample of the shape of the end of the outer bobbin;

FIG. 11 is a cross-sectional view along a plane perpendicular to thewinding axis direction of the structure of a transformer according to amodified example of embodiment 1;

FIG. 12 is a perspective view schematically depicting a modified exampleof the structure of a core according to embodiment 1;

FIG. 13 is an exploded perspective view of a transformer according toembodiment 2;

FIG. 14 is a cross-sectional view along a plane perpendicular to thewinding axis direction of the transformer according to embodiment 2;

FIG. 15 is a cross-sectional view along an XY plane depicting an exampleof the shape of an end of an outer bobbin;

FIG. 16 is an exploded perspective view of a transformer according toembodiment 3;

FIG. 17 is a cross-sectional view along a plane perpendicular to thewinding axis direction of the transformer according to embodiment 3;

FIG. 18 is an exploded perspective view of a transformer according toembodiment 4;

FIG. 19 is a cross-sectional view along a plane perpendicular to thewinding axis direction of the transformer according to embodiment 4;

FIG. 20 is an exploded perspective view of a transformer according toembodiment 5;

FIG. 21 is a cross-sectional view along a plane perpendicular to thewinding axis direction of the transformer according to embodiment 5;

FIG. 22 is a drawing depicting a modified example of the structure of acore according to embodiment 5;

FIG. 23 is a drawing depicting a modified example of the structure ofthe core according to embodiment 5;

FIG. 24 is a cross-sectional view along a plane perpendicular to thewinding axis direction of a coil device according to embodiment 5;

FIG. 25 is a circuit diagram depicting an example of a phase-shiftfull-bridge circuit;

FIG. 26 is a circuit diagram depicting an example of an LLC resonanthalf-bridge circuit;

FIG. 27 is a cross-sectional view depicting the structure of atransformer of a comparative example; and

FIG. 28 is a cross-sectional view depicting the structure of atransformer of another comparative example.

DETAILED DESCRIPTION Underlying Knowledge Forming Basis of the PresentDisclosure

First, the findings forming the basis of the present disclosure will bedescribed.

FIG. 27 depicts a transformer of a comparative example. In FIG. 27,winding 908 a and winding 908 b are primary windings, and winding 909 aand winding 909 b are secondary windings. In the transformer of FIG. 27,in order to improve the heat dissipating property of these windings,these windings are molded with a sealing resin 903 having high thermalconductivity.

FIG. 28 depicts a transformer of another comparative example. In FIG.28, an outer winding 912 is wound onto the outside of an inner winding911. Then, after these windings have been wound, the windings are moldedwith a thermosetting insulating resin having high thermal conductivity.In this transformer, the inner winding 911 functions as a primarywinding, and the outer winding 912 functions as a secondary winding. InFIG. 28, in order to handle winding-thickening that occurs when theinner winding 911 is wound onto an inner bobbin 914, an air layer isprovided between an outer bobbin 913 and the inner winding 911.

The transformer depicted in FIG. 27 has a problem in that the sealingresin 903 for increasing the heat dissipating property of the primarywindings and the secondary windings causes the weight of the transformerto increase.

The transformer depicted in FIG. 28 has a problem in that, in the casewhere winding pressure is applied to the outer bobbin 913 due to theouter winding 912 being wound around, the outer bobbin 913 bends towardthe air layer. If this bending becomes excessive, there is a risk of theouter bobbin 913 breaking.

The transformer depicted in FIG. 28 has a problem in that variation inthe winding-thickening or winding-thinning of the inner winding 911causes the distance between the inner winding 911 and the outer winding912 to vary, and leakage inductance therefore varies.

Thus, the present inventors examined a magnetic device in which a bobbinand a winding are brought into close contact. This magnetic deviceenables heat of the winding to be dissipated via the bobbin. Forexample, the sealing resin can be reduced or omitted to reduce weight ofthe device while maintaining a high heat dissipating property.

In consideration of the above, the present inventors arrived at thepresent disclosure.

Overview of Embodiments

A magnetic device according to one aspect of the present disclosure isprovided with a winding in which a conductive wire is wound around, anda bobbin arranged at the outer peripheral side of the winding. Thebobbin includes a first bobbin member and a second bobbin member, and anend of the first bobbin member opposes an end of the second bobbinmember. The winding and the first bobbin member are provided in contactwith each other, and the winding and the second bobbin member areprovided in contact with each other. A gap is provided between the endof the first bobbin member and the end of the second bobbin member inthe circumferential winding direction of the winding.

According to the present aspect, the winding and the first and secondbobbin members can be appropriately brought into contact even in thecase where the winding has become thicker and even in the case where thewinding has become thinner. Consequently, heat can be suitablydissipated via the first bobbin member and the second bobbin member evenwhen the winding generates heat. In the case where resin molding isomitted or reduced, the weight of the magnetic device can be reducedwhile securing the heat dissipating property of the winding.Furthermore, the distance between an inner winding and an outer windingis fixed to correspond to the bobbin thickness, and therefore leakageinductance is stable even in the case where the winding has becomethicker and even in the case where the winding has become thinner.

In the aforementioned aspect, the bobbin may further include a thirdbobbin member. The other end of the first bobbin member may oppose oneend of the third bobbin member. The other end of the second bobbinmember may oppose the other end of the third bobbin member. The windingand the third bobbin member may be provided in contact with each other.A gap may be provided between an end of the first bobbin member and anend of the third bobbin member in the circumferential winding directionof the winding. A gap may be provided between an end of the secondbobbin member and an end of the third bobbin member in thecircumferential winding direction of the winding.

It should be noted that the “first bobbin member” is an example of a“first insulator”, the “second bobbin member” is an example of a “secondinsulator”, and the “third bobbin member” is an example of a “thirdinsulator”.

In this case, the winding and the first, second, and third bobbinmembers can be appropriately brought into contact even in the case wherethe winding has become thicker and even in the case where the windinghas become thinner, and heat of the winding can be dissipated via thesebobbin members.

In the aforementioned aspect, the winding may be formed with theconductive wire being wound around in a shape including a short area anda long area. The end of the first bobbin member and the end of thesecond bobbin member may be located beside the short area of thewinding.

In this case, the long area of the winding and the first and secondbobbin members can be appropriately brought into contact. Thus, acomparatively large contact area can be secured, and heat of the windingcan be suitably dissipated via the first bobbin member and the secondbobbin member.

In the aforementioned aspect, the winding may be formed with theconductive wire being wound around in a shape including a short area anda long area. The end of the first bobbin member and the end of thesecond bobbin member may oppose a portion between the short area of thewinding and the long area of the winding.

In this case, the long area of the winding and the first bobbin membercan be appropriately brought into contact, and the short area of thewinding and the second bobbin member can be appropriately brought intocontact. Alternatively, the short area of the winding and the firstbobbin member can be appropriately brought into contact, and the longarea of the winding and the second bobbin member can be appropriatelybrought into contact. As a result, heat of the winding can be suitablydissipated via the first bobbin member and the second bobbin member evenin the case where there are variations in the winding action for thewinding.

It should be noted that the “long area of the winding” is an example ofa “first portion of the winding”, and the “short area of the winding” isan example of a “second portion of the winding”. Furthermore, the “longarea of the winding” is an example of a “linear portion of the winding”.The length of the long area and/or linear portion of the winding islonger than ¼ of the length of one turn of the winding, for example.

In the aforementioned aspect, the end of the first bobbin member and theend of the second bobbin member may have a stepped face.

In this case, the creepage distance from the inner circumferential sideto the outer circumferential side in the ends of the first and secondbobbin members can become longer. The insulating property can betherefore improved.

In the aforementioned aspect, one of the end of the first bobbin memberand the end of the second bobbin member may have a return structure thatengages with the other.

In this case, the first bobbin member and the second bobbin member canbe less likely to detach. As a result, it is possible to preventloosening in the case where a winding is wound around a bobbin.

A power conversion device according to one aspect of the presentdisclosure is provided with the magnetic device of any of theaforementioned aspects, and a power conversion circuit that is connectedto the winding.

According to the present aspect, heat generated in the winding by theoperation of the power conversion circuit can be suitably dissipated viathe first bobbin member and the second bobbin member.

Hereinafter, embodiments according to the present disclosure will bedescribed with reference to the drawings. It should be noted that thesame reference symbols are used for the same constituent elements in thedrawings.

It should be noted that the embodiments described hereinafter allrepresent comprehensive or specific examples. The numerical values, theshapes, the materials, the constituent elements, the arrangementpositions and modes of connection of the constituent elements, and thelike given in the following embodiments are examples and are notintended to restrict the present disclosure. Furthermore, constituentelements that are not described in the independent claims indicating themost significant concepts from among the constituent elements in thefollowing embodiments are described as optional constituent elements.

Embodiment 1

FIG. 1 is a perspective view schematically depicting the structure of atransformer 101 according to embodiment 1. FIG. 2 is a cross-sectionalview along a YZ plane including the winding axis of the transformer 101depicted in FIG. 1. FIG. 3 is an exploded perspective view depicting thetransformer 101 depicted in FIG. 1. FIG. 4 is a cross-sectional viewalong an XY plane perpendicular to the winding axis direction of thetransformer 101 depicted in FIG. 1. The transformer 101 is an example ofa “magnetic device” in the present disclosure.

The transformer 101 is used in a power conversion circuit such as aDC-DC converter. The structure of the transformer 101 will be describedusing FIGS. 1 to 4.

The transformer 101 is provided with an inner bobbin 102, an innerwinding 106, an outer bobbin 103, an outer winding 104, and a core 107.

The inner bobbin 102 is formed of an insulating resin, for example. Theinner bobbin 102 includes an inner column 102A extending in the windingaxis direction (i.e., Z direction), an inner upper flange 102B formed atone end of the inner column 102A, and an inner lower flange 102C formedat the other end. The inner column 102A may have a square column shape.

The inner winding 106 is formed of a conductive wire such as a singlewire or a litz wire. The inner winding 106 is wound onto the innerbobbin 102. As depicted in FIG. 4, the inner winding 106 is formed withthe conductive wire being wound around, in a shape having a short areaSA parallel to the Y direction and a long area LA parallel to the Xdirection.

The outer bobbin 103 is formed of an insulating resin, for example. Theouter bobbin 103 includes a first bobbin member 103X and a second bobbinmember 103Y. The first bobbin member 103X and the second bobbin member103Y have the same shape, and are formed in a squared U-shape whenviewed from the Z direction. The ends of the first bobbin member 103Xoppose the ends of the second bobbin member 103Y. Gaps 105 are providedbetween the ends of the first bobbin member 103X and the ends of thesecond bobbin member 103Y in the winding direction of the inner winding106. The size of the gaps 105 may be larger than 0 mm and equal to orless than 3 mm, for example.

The first bobbin member 103X and the second bobbin member 103Y eachinclude an outer column 103A extending in the winding axis direction(i.e., Z direction), an outer upper flange 103B formed at one end of theouter column 103A, and an outer lower flange 103C formed at the otherend. The outer columns 103A and 103B constitutes a square column bybeing assembled. The shape of the ends of the first bobbin member 103Xand the ends of the second bobbin member 103Y are described later on.

The outer winding 104 is formed of a conductive wire such as a singlewire or a litz wire. The outer winding 104 is wound onto the outerbobbin 103.

The core 107 is formed of a magnetic material such as a ferrite, a dustcore, or an amorphous alloy. The core 107 includes a core 107A and acore 107B. The core 107A and the core 107B have the same shape, and areformed in an E-shape when viewed from the X direction. Hereinafter, thecore 107A and the core 107B are sometimes collectively referred to asthe core 107.

The gaps 105 in the outer bobbin 103 are located beside the short areasof the inner winding 106, as depicted in FIG. 4. The outer bobbin 103and the long areas of the inner winding 106 are thereby in contact witheach other.

When the transformer 101 is assembled, first, the inner winding 106 iswound onto the inner column 102A of the inner bobbin 102. Next, theouter bobbin 103 is arranged by being made to slide along the XY planesuch that the outer column 103A comes into contact with the innerwinding 106. Next, the outer winding 104 is wound onto the outer column103A. Finally, the core 107 is arranged by being made to slide along theZY plane.

The gaps 105 in the outer bobbin 103 become larger as the inner winding106 becomes thicker, and the gaps 105 becomes smaller as the innerwinding 106 becomes thinner. Therefore, in either case, the pair of longareas of the inner winding 106 and the outer bobbin 103 areappropriately in contact. As a result, heat of the inner winding 106 canbe suitably transmitted to the outer bobbin 103, and thus the heatdissipating property of the inner winding 106 can be improved.

Next, an example will be described in which the results of a thermalanalysis of windings in a coil device according to the presentembodiment and a coil device according to a comparative example arecompared.

FIG. 5 depicts a temperature distribution along a YZ plane that includesthe winding axis in the coil device having the structure of thecomparative example. FIG. 6 depicts a temperature distribution along aYZ plane that includes the winding axis in the coil device according tothe present embodiment.

In the thermal analysis depicted in FIG. 6, a coil device having thestructure depicted in FIG. 4 was used as the coil device according tothe present embodiment. This coil device has gaps beside short areas ofa winding. Long areas of a winding 112 and a bobbin 111 are therefore incontact.

Meanwhile, a coil device having a structure such as that depicted inFIG. 28 was used as the coil device according to the comparativeexample. In the coil device used in the thermal analysis of FIG. 5, gapsare not provided in joining parts 915 of the outer bobbin 913, and anair layer 114 is provided between the winding 112 and the bobbin 111.

In FIGS. 5 and 6, a thermal analysis was carried out without there beinga core or an outer winding. In both of the coil devices, a loss of 10 Wwas given for the inner winding. The ambient temperature was 25° C. Aheat sink 113 was arranged so as to be in contact with the bottom faceof the coil devices, and the temperature of the heat sink 113 was 15° C.

In FIG. 5, the highest value of the temperature of the winding 112reaches 47.5° C., whereas, in FIG. 6, the highest value of thetemperature of the winding 112 is suppressed to 37.5° C. From theseresults, it is apparent that, in the structure of the presentembodiment, a rise in the temperature of the winding can be suppressedcompared to the structure of the comparative example.

FIGS. 7 and 8 are cross-sectional views along an XY plane depictingexamples of the shape of an end 103Xt of the first bobbin member 103Xand an end 103Yt of the second bobbin member 103Y.

In FIG. 7, the end 103Xt of the first bobbin member 103X includes a baseend 103Xa and a protrusion 103Xb that protrudes from the base end 103Xa.The end 103Yt of the second bobbin member 103Y includes a base end 103Yaand a protrusion 103Yb that protrudes from the base end 103Ya. The end103Xt of the first bobbin member 103X and the end 103Yt of the secondbobbin member 103Y oppose each other.

Specifically, the protrusion 103Xb of the first bobbin member 103X andthe base end 103Ya of the second bobbin member 103Y oppose each otherthrough the gap 105, and the protrusion 103Yb of the second bobbinmember 103Y and the base end 103Xa of the first bobbin member 103Xoppose each other through the gap 105. Furthermore, the protrusion 103Xbof the first bobbin member 103X and the protrusion 103Yb of the secondbobbin member 103Y abut in the X direction.

To paraphrase, the end 103Xt of the first bobbin member 103X has astepped end face that includes an end face of the base end 103Xa and anend face and a side face of the protrusion 103Xb. The end 103Yt of thesecond bobbin member 103Y has a stepped end face that includes an endface of the base end 103Ya and an end face and a side face of theprotrusion 103Yb. These two stepped end faces oppose each other.

In FIG. 8, the end 103Xt of the first bobbin member 103X includes aninclined end face 103Xc between the base end 103Xa and the protrusion103Xb. The end 103Yt of the second bobbin member 103Y includes aninclined end face 103Yc between the base end 103Ya and the protrusion103Yb.

In FIG. 8, the protrusion 103Xb of the first bobbin member 103X and thebase end 103Ya of the second bobbin member 103Y oppose each otherthrough the gap 105, and the protrusion 103Yb of the second bobbinmember 103Y and the base end 103Xa of the first bobbin member 103Xoppose each other through the gap 105. Furthermore, the inclined endface 103Xc of the first bobbin member 103X and the inclined end face103Yc of the second bobbin member 103Y oppose each other through the gap105.

To paraphrase, the end 103Xt of the first bobbin member 103X has astepped end face that includes the end face of the base end 103Xa, theend face of the protrusion 103Xb, and the inclined end face 103Xc. Theend 103Yt of the second bobbin member 103Y has a stepped end face thatincludes the end face of the base end 103Ya, the end face of theprotrusion 103Yb, and the inclined end face 103Yc. These two stepped endfaces oppose each other.

Due to the end 103Xt of the first bobbin member 103X and the end 103Ytof the second bobbin member 103Y each having a stepped end face asdepicted in FIGS. 7 and 8, the creepage distance of the outer bobbin 103between the inner winding 106 and the outer winding 104 can belengthened without losing the heat dissipating property of the innerwinding 106. As a result, the insulating property can be improved.

FIGS. 9 and 10 are cross-sectional views along the XY plane depictingother examples of the shape of the end 103Xt of the first bobbin member103X and the end 103Yt of the second bobbin member 103Y.

In FIG. 9, the protrusion 103Xb of the first bobbin member 103Xincludes, at a tip thereof, an engaging part 103Xd that extends in the Xdirection. The protrusion 103Yb of the second bobbin member 103Yincludes, at a tip thereof, a semicircular engaging part 103Yd that isformed protruding in the X direction.

In FIG. 9, the protrusion 103Xb of the first bobbin member 103X and thebase end 103Ya of the second bobbin member 103Y oppose each otherthrough the gap 105, and the protrusion 103Yb of the second bobbinmember 103Y and the base end 103Xa of the first bobbin member 103Xoppose each other through the gap 105.

In FIG. 9, as the gaps 105 widens, the engaging part 103Xd of the firstbobbin member 103X and the engaging part 103Yd of the second bobbinmember 103Y engage.

To paraphrase, the end 103Xt of the first bobbin member 103X has arecess defined by the base end 103Xa, the protrusion 103Xb, and theengaging part 103Xd. The end 103Yt of the second bobbin member 103Y hasa protrusion serving as the engaging part 103Yd. The protrusion of theend 103Yt of the second bobbin member 103Y engages with the recess inthe end 103Xt of the first bobbin member 103X.

The structure depicted in FIG. 10 is different from the structuredepicted in FIG. 9 only in that the engaging part 103Yd of the secondbobbin member 103Y is formed in a triangular shape.

Due to the engaging part 103Xd being provided in the end 103Xt of thefirst bobbin member 103X and the engaging part 103Yd being provided inthe end 103Yt of the second bobbin member 103Y as depicted in FIGS. 9and 10, the second bobbin member 103Y can be less likely to detach fromfirst bobbin member 103X when the outer winding 104 is wound.Furthermore, the creepage distance of the outer bobbin 103 between theinner winding 106 and the outer winding 104 can be lengthened withoutlosing the heat dissipating property of the inner winding 106. As aresult, the insulating property can be improved.

FIG. 11 is a cross-sectional view along an XY plane perpendicular to thewinding axis direction of a transformer 101A according to a modifiedexample of the present embodiment. In FIG. 11, the inner winding 106 isformed with a conductive wire being wound around, in a shape havingarc-shaped areas that have a chord extending in the Y direction, andlong areas extending in the X direction. It should be noted that thearc-shaped areas of the inner winding 106 are an example of a “corner”.Furthermore, the first bobbin member 103X and the second bobbin member103Y have the same shape, and are formed in a U-shape when viewed fromthe Z direction. The outer bobbin 103 and the inner winding 106 are inclose contact at linear portions, and therefore the same effect as thatof the transformer 101 can be obtained also in a case such as this.

As described above, in embodiment 1, a pair of linear portions (e.g., apair of long areas) of the outer bobbin 103 and the inner winding 106are in close contact. Therefore, bending is less likely to occur in theouter bobbin 103 and the possibility of the outer bobbin 103 breakingcan be reduced even in the case where winding pressure is applied to theouter bobbin 103 when the outer winding 104 is wound around the outerbobbin 103.

The gaps 105 in the outer bobbin 103 become smaller in the case wherethe inner winding 106 becomes thinner due to variation that occurs whenwinding is performed. The gaps 105 in the outer bobbin 103 become largerin the case where the inner winding 106 becomes thicker due to variationthat occurs when winding is performed. In either case, the distancebetween the inner winding 106 and the outer winding 104 is fixed tocorrespond to the thickness of the outer bobbin 103. It is thereforepossible to reduce variation in leakage inductance. Furthermore, abobbin having a structure same as or similar to the outer bobbin 103 maybe additionally arranged outside of the outer winding 104. It is therebypossible to also improve the heat dissipating property of the outerwinding 104.

The transformer 101 may not have the core 107.

The core 107 depicted in FIG. 3 is made up of the two E-shaped cores107A and 107B, but there is no restriction thereto. For example, thecore 107 may be made up of an E-shaped core and an I-shaped core.

FIG. 12 is a perspective view schematically depicting another exampleconfiguration of the core. As depicted in FIG. 12, the central leg ofthe core is divided, and a structure is possible in which one pair ofcores 109 having a squared U-shape when viewed from the X direction arefit together in the Z direction, and two pairs of such cores 109 aremade to abut in the Y direction.

In the example depicted in FIG. 4, the winding axis of the inner winding106 and the winding axis of the outer winding 104 are shared, but thereis no restriction thereto, and a central axis that is different from theinner winding 106 and the outer winding 104 may be shared.

Embodiment 2

A designer can design various bobbins on the basis of the designprinciples described in relation to embodiment 1. In embodiment 2, amagnetic device provided with two bobbin members arranged with gapstherebetween is described.

FIG. 13 is an exploded perspective view of a transformer 101B accordingto embodiment 2. FIG. 14 is a cross-sectional view along an XY planeperpendicular to the winding axis direction of the transformer 101B. Itshould be noted that a cross-sectional view along a YZ plane thatincludes the winding axis of the transformer 101B is the same as FIG. 2.The transformer 101B is an example of a “magnetic device” in the presentdisclosure. The structure of the transformer 101B of embodiment 2 willbe described using FIGS. 2, 13, and 14.

The transformer 101B is provided with an inner bobbin 102, an innerwinding 106, an outer bobbin 103, an outer winding 104, and a core 107.

The inner bobbin 102 is formed of an insulating resin, for example. Theinner bobbin 102 includes an inner column 102A extending in the windingaxis direction (i.e., Z direction), an inner upper flange 102B formed atone end of the inner column 102A, and an inner lower flange 102C formedat the other end.

The inner winding 106 is formed of a conductive wire such as a singlewire or a litz wire. The inner winding 106 is wound onto the innerbobbin 102. As depicted in FIG. 14, the inner winding 106 is formed withthe conductive wire being wound around, in a shape having short areasparallel to the Y direction and long areas parallel to the X direction.

The outer bobbin 103 is formed of an insulating resin, for example. Theouter bobbin 103 includes a first bobbin member 103P, a second bobbinmember 103Q, and a third bobbin member 103R. The first bobbin member103P and the second bobbin member 103Q are formed in an L-shape whenviewed from the Z direction. The third bobbin member 103R is formed inan I-shape when viewed from the Z direction.

One end of the first bobbin member 103P opposes one end of the secondbobbin member 103Q. The other end of the first bobbin member 103Popposes one end of the third bobbin member 103R. The other end of thesecond bobbin member 103Q opposes the other end of the third bobbinmember 103R. Gaps 105 are provided between the ends of the bobbinmembers in the winding direction of the inner winding 106.

The first bobbin member 103P, the second bobbin member 103Q, and thethird bobbin member 103R each include an outer column 103A extending inthe winding axis direction (i.e., Z direction), an outer upper flange103B formed at one end of the outer column 103A, and an outer lowerflange 103C formed at the other end. The outer columns 103A of the firstto third bobbin members 103P, 103Q, and 103R constitutes a square columnby being assembled.

The outer winding 104 is formed of a conductive wire such as a singlewire or a litz wire. The outer winding 104 is wound onto the outerbobbin 103.

The core 107 is formed of a magnetic material such as a ferrite, a dustcore, or an amorphous alloy. The core 107 includes a core 107A and acore 107B. The core 107A and the core 107B each have the same shape, andare formed in an E-shape when viewed from the X direction. Hereinafter,the core 107A and the core 107B are sometimes collectively referred toas the core 107.

As depicted in FIG. 14, the gap 105 between the first bobbin member 103Pand the second bobbin member 103Q is located beside a first short areaof the inner winding 106. As depicted in FIG. 14, the gap 105 betweenthe first bobbin member 103P and the third bobbin member 103R is locatedbeside a corner between a second short area and a first long area of theinner winding 106, and the gap 105 between the second bobbin member 103Qand the third bobbin member 103R is located beside a corner between thesecond short area and a second long area of the inner winding 106. Theouter bobbin 103 and the inner winding 106 are thereby in contact witheach other at the long areas of the inner winding 106 and the secondshort area in FIG. 14.

When the transformer 101B is assembled, first, the inner winding 106 iswound onto the inner column 102A of the inner bobbin 102. Next, theouter bobbin 103 is arranged by being made to slide along the XY planesuch that the outer column 103A comes into contact with the innerwinding 106. Next, the outer winding 104 is wound onto the outer column103A. Finally, the core 107 is arranged by being made to slide along theZY plane.

The gaps 105 in the outer bobbin 103 become larger as the inner winding106 becomes thicker, and the gaps 105 becomes smaller as the innerwinding 106 becomes thinner. In either case, the pair of long areas andone short area of the inner winding 106 and the outer bobbin 103 areappropriately in contact. As a result, heat of the inner winding 106 canbe suitably transmitted to the outer bobbin 103, and thereby the heatdissipating property of the inner winding 106 can be improved.

FIG. 15 is a cross-sectional view along the XY plane depicting anexample of the shape of an end 103Pt of the first bobbin member 103P andan end 103Rt of the third bobbin member 103R.

In FIG. 15, the end 103Pt of the first bobbin member 103P includes abase end 103Pa and a protrusion 103Pb that protrudes from the base end103Pa. The end 103Rt of the third bobbin member 103R includes a base end103Ra and a protrusion 103Rb that protrudes from the base end 103Ra. Theend 103Pt of the first bobbin member 103P and the end 103Rt of the thirdbobbin member 103R oppose each other.

Specifically, the protrusion 103Pb of the first bobbin member 103P andthe base end 103Ra of the third bobbin member 103R oppose each otherthrough the gap 105, and the protrusion 103Rb of the third bobbin member103R and the base end 103Pa of the first bobbin member 103P oppose eachother through the gap 105. Furthermore, the protrusion 103Pb of thefirst bobbin member 103P and the protrusion 103Rb of the third bobbinmember 103R are adjacent in the Y direction.

To paraphrase, the end 103Pt of the first bobbin member 103P has astepped end face that includes an end face of the base end 103Pa and anend face and a side face of the protrusion 103Pb. The end 103Rt of thethird bobbin member 103R has a stepped end face that includes an endface of the base end 103Ra and an end face and a side face of theprotrusion 103Rb. These two stepped end faces oppose each other.

Due to the end 103Pt of the first bobbin member 103P and the end 103Rtof the third bobbin member 103R each having a stepped end face asdepicted in FIG. 15, the creepage distance of the outer bobbin 103between the inner winding 106 and the outer winding 104 can belengthened without losing the heat dissipating property of the innerwinding 106. As a result, the insulating property can be improved.

It should be noted that, in embodiment 2, the shape described withreference to FIGS. 7 to 10 may be adopted for the shape of the end 103Ptof the first bobbin member 103P and an end 103Qt of the second bobbinmember 103Q. The same effect can be obtained by means of these shapes.Furthermore, a shape such as that depicted in FIG. 11 may be adoptedalso for the shape of the transformer 101B of embodiment 2. The sameeffect can be obtained also with this shape.

As described above, in embodiment 2, the outer bobbin 103 is made up ofthe three bobbin members 103P, 103Q, and 103R. Compared to the examplegiven in embodiment 1, the contact area can be thereby increased by anamount corresponding to the short area of the inner winding 106 cominginto contact with the outer bobbin 103. Therefore, according toembodiment 2, the heat dissipating property can be further improvedcompared to embodiment 1.

The outer bobbin 103 and linear portions (e.g., long areas) of the innerwinding 106 are in close contact. With this configuration, bending isless likely to occur in the outer bobbin 103 even in the case wherewinding pressure is applied to the outer bobbin 103 when the outerwinding 104 is wound around the outer bobbin 103. Therefore, thepossibility of the outer bobbin 103 breaking can be reduced.

The distance between the inner winding 106 and the outer winding 104 isfixed to correspond to the thickness of the outer bobbin 103. It istherefore possible to reduce variation in leakage inductance.Furthermore, a bobbin having a structure same as or similar to the outerbobbin 103 may be additionally arranged outside of the outer winding104. It is thereby possible to also improve the heat dissipatingproperty of the outer winding 104.

The transformer 101B may not have the core 107.

The core 107 depicted in FIG. 13 is made up of the two E-shaped cores107A and 107B, but there is no restriction thereto. The core 107 may bemade up of four squared U-shaped cores, for example. Alternatively, thecore 107 may be made up of an E-shaped core and an I-shaped core.

In the example depicted in FIG. 14, the winding axis of the innerwinding 106 and the winding axis of the outer winding 104 are shared,but there is no restriction thereto, and a central axis that isdifferent from the inner winding 106 and the outer winding 104 may beshared.

Embodiment 3

A designer can design various bobbins on the basis of the designprinciples described in relation to embodiment 1. In embodiment 3, amagnetic device provided with four bobbin members arranged with gapstherebetween is described.

FIG. 16 is an exploded perspective view of a transformer 101C accordingto embodiment 3. FIG. 17 is a cross-sectional view along an XY planeperpendicular to the winding axis direction of the transformer 101C. Itshould be noted that a cross-sectional view along a YZ plane thatincludes the winding axis of the transformer 101C is the same as FIG. 2.The structure of the transformer 101C of embodiment 3 will be describedusing FIGS. 2, 16, and 17.

The transformer 101C is provided with an inner bobbin 102, an innerwinding 106, an outer bobbin 103, an outer winding 104, and a core 107.

The inner bobbin 102 is formed of an insulating resin, for example. Theinner bobbin 102 includes an inner column 102A extending in the windingaxis direction (i.e., Z direction), an inner upper flange 102B formed atone end of the inner column 102A, and an inner lower flange 102C formedat the other end.

The inner winding 106 is formed of a conductive wire such as a singlewire or a litz wire. The inner winding 106 is wound onto the innerbobbin 102. As depicted in FIG. 17, the inner winding 106 is formed withthe conductive wire being wound around, in a shape having short areasparallel to the Y direction and long areas parallel to the X direction.

The outer bobbin 103 is formed of an insulating resin, for example. Theouter bobbin 103 includes a first bobbin member 103I, a second bobbinmember 103J, a third bobbin member 103K, and a fourth bobbin member103L. The first to fourth bobbin members 103I, 103J, 103K, and 103L areformed in L-shapes when viewed from the Z direction.

One end of the first bobbin member 103I opposes one end of the secondbobbin member 103J. The other end of the first bobbin member 103Iopposes one end of the third bobbin member 103K. The other end of thesecond bobbin member 103J opposes one end of the fourth bobbin member103L. The other end of the third bobbin member 103K opposes the otherend of the fourth bobbin member 103L. Gaps 105 are provided between theends of the bobbin members in the winding direction of the inner winding106.

The first to fourth bobbin members 103I, 103J, 103K, and 103L eachinclude an outer column 103A extending in the winding axis direction(i.e., Z direction), an outer upper flange 103B formed at one end of theouter column 103A, and an outer lower flange 103C formed at the otherend. The outer columns 103A of the first to fourth bobbin members 103I,103J, 103K, and 103L constitutes a square column by being assembled.

The outer winding 104 is formed of a conductive wire such as a singlewire or a litz wire. The outer winding 104 is wound onto the outerbobbin 103.

The core 107 is formed of a magnetic material such as a ferrite, a dustcore, or an amorphous alloy. The core 107 includes a core 107A and acore 107B. The core 107A and the core 107B each have the same shape, andare formed in an E-shape when viewed from the X direction. Hereinafter,the core 107A and the core 107B are sometimes collectively referred toas the core 107.

As depicted in FIG. 17, the gap 105 between the first bobbin member 103Iand the second bobbin member 103J is located beside a first long area ofthe inner winding 106; the gap 105 between the third bobbin member 103Kand the fourth bobbin member 103L is located beside a second long areaof the inner winding 106; the gap 105 between the first bobbin member103I and the third bobbin member 103K is located beside a first shortarea of the inner winding 106; and the gap 105 between the second bobbinmember 103J and the fourth bobbin member 103L is located beside a secondshort area of the inner winding 106.

When the transformer 101C is assembled, first, the inner winding 106 iswound onto the inner column 102A of the inner bobbin 102. Next, theouter bobbin 103 is arranged by being made to slide along the XY planesuch that the outer column 103A comes into contact with the innerwinding 106. Next, the outer winding 104 is wound onto the outer column103A. Finally, the core 107 is arranged by being made to slide along theZY plane.

The gaps 105 in the outer bobbin 103 become larger as the inner winding106 becomes thicker, and the gaps 105 becomes smaller as the innerwinding 106 becomes thinner. In either case, L-shaped areas, eachincluding a corner, of the inner winding 106 and the outer bobbin 103are appropriately in contact. As a result, heat of the inner winding 106can be suitably transmitted to the outer bobbin 103, and thereby theheat dissipating property of the inner winding 106 can be improved.

It should be noted that, in embodiment 3, the shape described withreference to FIGS. 7 to 10 may be adopted for the shape of the ends ofthe first to fourth bobbin members 103I, 103J, 103K, and 103L. The sameeffect can be obtained by means of these shapes. Furthermore, a shapesuch as that depicted in FIG. 11 may be adopted also for the shape ofthe transformer 101C in embodiment 3. The same effect can be obtainedalso with this shape.

As described above, in embodiment 3, the outer bobbin 103 is made up ofthe four bobbin members 103I, 103J, 103K, and 103L. The contact areabetween the inner winding 106 and the outer bobbin 103 thereby increasescompared to embodiment 1. Therefore, according to embodiment 3, the heatdissipating property can be further improved compared to embodiment 1.Furthermore, the outer bobbin 103 of embodiment 2 is made up of twotypes of bobbin members; however, the outer bobbin 103 of embodiment 3may be made up of one type of bobbin member, for example. The types ofcomponents can thereby be lessened.

The outer bobbin 103 and L-shaped areas, each including a corner, of theinner winding 106 are in close contact. With this configuration, bendingis less likely to occur in the outer bobbin 103 even in the case wherewinding pressure is applied to the outer bobbin 103 when the outerwinding 104 is wound around the outer bobbin 103. Therefore, thepossibility of the outer bobbin 103 breaking can be reduced.

The distance between the inner winding 106 and the outer winding 104 isfixed to correspond to the thickness of the outer bobbin 103. It istherefore possible to reduce variation in leakage inductance.Furthermore, a bobbin having a structure same as or similar to the outerbobbin 103 may be additionally arranged outside of the outer winding104. It is thereby possible to also improve the heat dissipatingproperty of the outer winding 104.

The transformer 101C may not have the core 107.

The core 107 depicted in FIG. 16 is made up of the two E-shaped cores107A and 107B, but there is no restriction thereto. The core 107 may bemade up of four squared U-shaped cores, for example. Alternatively, thecore 107 may be made up of an E-shaped core and an I-shaped core.

In the example depicted in FIG. 17, the winding axis of the innerwinding 106 and the winding axis of the outer winding 104 are shared,but there is no restriction thereto, and a central axis that isdifferent from the inner winding 106 and the outer winding 104 may beshared.

Embodiment 4

A designer can design various bobbins on the basis of the designprinciples described in relation to embodiment 1. In embodiment 4, amagnetic device provided with two L-shaped bobbin members arranged withgaps therebetween is described.

FIG. 18 is an exploded perspective view of a transformer 101D accordingto embodiment 4. FIG. 19 is a cross-sectional view along an XY planeperpendicular to the winding axis direction of the transformer 101D. Itshould be noted that a cross-sectional view along a YZ plane thatincludes the winding axis of the transformer 101D is the same as FIG. 2.The structure of the transformer 101D of embodiment 4 will be describedusing FIGS. 2, 18, and 19.

The transformer 101D is provided with an inner bobbin 102, an innerwinding 106, an outer bobbin 103, an outer winding 104, and a core 107.

The inner bobbin 102 is formed of an insulating resin, for example. Theinner bobbin 102 includes an inner column 102A extending in the windingaxis direction (i.e., Z direction), an inner upper flange 102B formed atone end of the inner column 102A, and an inner lower flange 102C formedat the other end.

The inner winding 106 is formed of a conductive wire such as a singlewire or a litz wire. The inner winding 106 is wound onto the innerbobbin 102. As depicted in FIG. 19, the inner winding 106 is formed withthe conductive wire being wound around, in a shape having short areasparallel to the Y direction and long areas parallel to the X direction.

The outer bobbin 103 is formed of an insulating resin, for example. Theouter bobbin 103 includes a first bobbin member 103M and a second bobbinmember 103N. The first and second bobbin members 103M and 103N have thesame shape and are formed in an L-shape when viewed from the Zdirection.

One end of the first bobbin member 103M opposes one end of the secondbobbin member 103N. The other end of the first bobbin member 103Mopposes the other end of the second bobbin member 103N. Gaps 105 areprovided between the ends of the bobbin members in the winding directionof the inner winding 106.

The first and second bobbin members 103M and 103N each include an outercolumn 103A extending in the winding axis direction (i.e., Z direction),an outer upper flange 103B formed at one end of the outer column 103A,and an outer lower flange 103C formed at the other end. The outercolumns 103A and 103B constitutes a square column by being assembled.

The outer winding 104 is formed of a conductive wire such as a singlewire or a litz wire. The outer winding 104 is wound onto the outerbobbin 103.

The core 107 is formed of a magnetic material such as a ferrite, a dustcore, or an amorphous alloy. The core 107 includes a core 107A and acore 107B. The core 107A and the core 107B each have the same shape, andare formed in an E-shape when viewed from the X direction. Hereinafter,the core 107A and the core 107B are sometimes collectively referred toas the core 107.

As depicted in FIG. 19, a first gap 105 is located beside a first corner(e.g., top-left corner) of the inner winding 106, and a second gap 105is located beside a second corner (e.g., the bottom-right corner) of theinner winding 106. The first and second corners each are located betweena long area and a short area of the inner winding 106.

When the transformer 101D is assembled, first, the inner winding 106 iswound onto the inner column 102A of the inner bobbin 102. Next, theouter bobbin 103 is arranged by being made to slide along the XY planesuch that the outer column 103A comes into contact with the innerwinding 106. Next, the outer winding 104 is wound onto the outer column103A. Finally, the core 107 is arranged by being made to slide along theZY plane.

The gaps 105 in the outer bobbin 103 become larger as the inner winding106 becomes thicker, and the gaps 105 becomes smaller as the innerwinding 106 becomes thinner. In either case, the outer bobbin 103 and anL-shaped area from the upper long area of the inner winding 106 to theright-side short area are appropriately in contact, and the outer bobbin103 and an L-shaped area from the left-side short area of the innerwinding 106 to the lower long area are appropriately in contact in FIG.19. As a result, heat of the inner winding 106 can be suitablytransmitted to the outer bobbin 103, and thereby the heat dissipatingproperty of the inner winding 106 can be improved.

It should be noted that, in embodiment 4, the shape described withreference to FIG. 15 may be adopted for the shape of the ends of thefirst and second bobbin members 103M and 103N. The same effect can beobtained by means of these shapes. Furthermore, the ends of the firstand second bobbin members 103M and 103N may have engaging parts 103 suchas those described with reference to FIGS. 9 and 10. The same effect canbe obtained by means of these shapes. Furthermore, a shape such as thatdepicted in FIG. 11 may be adopted also for the shape of the transformer101D in embodiment 4. The same effect can be obtained also with thisshape.

As described above, in embodiment 4, the gaps 105 are provided atcorners of the outer bobbin 103. In embodiment 4, the contact areabetween the inner winding 106 and the outer bobbin 103 thereby increasescompared to embodiment 1. Therefore, according to embodiment 4, the heatdissipating property can be further improved compared to embodiment 1.

The outer bobbin 103 and linear portions (e.g., long areas and shortareas) of the inner winding 106 are in close contact. With thisconfiguration, bending is less likely to occur in the outer bobbin 103even in the case where winding pressure is applied to the outer bobbin103 when the outer winding 104 is wound around the outer bobbin 103.Therefore, the possibility of the outer bobbin 103 breaking can bereduced.

The distance between the inner winding 106 and the outer winding 104 isfixed to correspond to the thickness of the outer bobbin 103. It istherefore possible to reduce variation in leakage inductance.Furthermore, a bobbin having a structure same as or similar to the outerbobbin 103 may be additionally arranged outside of the outer winding104. It is thereby possible to also improve the heat dissipatingproperty of the outer winding 104.

The transformer 101D may not have the core 107.

The core 107 depicted in FIG. 18 is made up of the two E-shaped cores107A and 107B, but there is no restriction thereto. The core 107 may bemade up of four squared U-shaped cores, for example. Alternatively, thecore 107 may be made up of an E-shaped core and an I-shaped core.

In the example depicted in FIG. 19, the winding axis of the innerwinding 106 and the winding axis of the outer winding 104 are shared,but there is no restriction thereto, and a central axis that isdifferent from the inner winding 106 and the outer winding 104 may beshared.

Embodiment 5

A designer can design various bobbins on the basis of the designprinciples described in relation to embodiment 1. In embodiment 5, amagnetic device provided with an inner bobbin made up of two bobbinmembers arranged with gaps therebetween, and an outer bobbin made up oftwo bobbin members arranged with gaps therebetween is described.

FIG. 20 is an exploded perspective view of a transformer 101E accordingto embodiment 5. FIG. 21 is a cross-sectional view along an XY planeperpendicular to the winding axis direction of the transformer 101E. Itshould be noted that a cross-sectional view along a YZ plane thatincludes the winding axis of the transformer 101E is the same as FIG. 2.The structure of the transformer 101E of embodiment 5 will be describedusing FIGS. 2, 20, and 21.

The transformer 101E is provided with a core 108, a core 109, an innerbobbin 102, an inner winding 106, an outer bobbin 103, and an outerwinding 104.

The core 108 has a column portion 108A and a bottom portion 108B, and isformed in a T-shape when viewed from the X direction. The core 109 has aside portion 109A and a top portion 109B, and is formed in a squaredU-shape when viewed from the X direction. The cores 108 and 109 areformed of a magnetic material such as a ferrite, a dust core, or anamorphous alloy. Hereinafter, the core 108 and the core 109 aresometimes collectively referred to as the core 107.

The inner bobbin 102 is formed of an insulating resin, for example. Theinner bobbin 102 includes a first bobbin member 102X and a second bobbinmember 102Y. The first and second bobbin members 102X and 102Y have thesame shape, and are formed in a squared U-shape when viewed from the Zdirection.

One end of the first bobbin member 102X opposes one end of the secondbobbin member 102Y. The other end of the first bobbin member 102Xopposes the other end of the second bobbin member 102Y. Gaps 105A areprovided between the ends of the bobbin members in the winding directionof the inner winding 106.

The first and second bobbin members 102X and 102Y each include an innercolumn 102A extending in the winding axis direction (i.e., Z direction),an inner upper flange 102B formed at one end of the inner column 102A,and an inner lower flange 102C formed at the other end.

The inner winding 106 is formed of a conductive wire such as a singlewire or a litz wire. The inner winding 106 is wound onto the innerbobbin 102. As depicted in FIG. 21, the inner winding 106 is formed withthe conductive wire being wound around, in a shape having short areasparallel to the Y direction and long areas parallel to the X direction.

The outer bobbin 103 is formed of an insulating resin, for example. Theouter bobbin 103 includes a first bobbin member 103X and a second bobbinmember 103Y. The first and second bobbin members 103X and 103Y have thesame shape, and are formed in a squared U-shape when viewed from the Zdirection.

The first and second bobbin members 103X and 103Y each include an outercolumn 103A extending in the winding axis direction (i.e., Z direction),an outer upper flange 103B formed at one end of the outer column 103A,and an outer lower flange 103C formed at the other end. In other words,the first and second bobbin members 103X and 103Y are formed in the samemanner as the first and second bobbin members 103X and 103Y ofembodiment 1 depicted in FIGS. 1 to 4.

The outer winding 104 is formed of a conductive wire such as a singlewire or a litz wire. The outer winding 104 is wound onto the outerbobbin 103.

As depicted in FIG. 21, the gaps 105A in the inner bobbin 102 arerespectively located beside the short areas of the inner winding 106.Furthermore, the gaps 105 in the outer bobbin 103 are respectivelylocated beside the short areas of the inner winding 106.

When the transformer 101E is assembled, first, the inner bobbin 102 isarranged by being made to slide from the Y direction such that the innercolumn 102A of the inner bobbin 102 comes into contact with the columnportion 108A of the core 108. Next, the inner winding 106 is wound ontothe inner column 102A of the inner bobbin 102. Next, the outer bobbin103 is arranged by being made to slide along the XY plane such that theouter column 103A comes into contact with the inner winding 106. Next,the outer winding 104 is wound onto the outer column 103A. Finally, thecore 109 is arranged such that the side portion 109A of the core 109comes into contact with the bottom portion 108B of the core 108 from theZ direction, and the top portion 109B comes into contact with the columnportion 108A.

By adjusting the size of the gaps 105A, the inner bobbin 102 can bebrought into contact with the core 108 in an appropriate manner even inthe case where the size of the first and second bobbin members 102X and102Y with respect to the core 107 has changed due to manufacturingvariations. Consequently, heat of the inner bobbin 102 can be suitablytransmitted to the core 108. As a result, heat absorbed from the innerwinding 106 by the inner bobbin 102 can be efficiently transmitted, andthereby the heat dissipating property of the inner winding 106 can beimproved.

According to embodiment 5, similar to embodiment 1, heat of the innerwinding 106 can be suitably transmitted to the outer bobbin 103, andthereby the heat dissipating property of the inner winding 106 can beimproved.

It should be noted that the shape described with reference to FIGS. 7 to10 may be adopted for the shape of the ends of the first and secondbobbin members 103X and 103Y in embodiment 5. The same effect can beobtained by means of these shapes. Furthermore, a shape such as thatdepicted in FIG. 11 may be adopted also for the shape of the transformer101E in embodiment 5. The same effect can be obtained also with thisshape.

The outer bobbin 103 and the linear portions (e.g., the long areas) ofthe inner winding 106 are in close contact. With this configuration,bending is less likely to occur in the outer bobbin 103 even in the casewhere winding pressure is applied to the outer bobbin 103 when the outerwinding 104 is wound around the outer bobbin 103. Therefore, thepossibility of the outer bobbin 103 breaking can be reduced.

The distance between the inner winding 106 and the outer winding 104 isfixed to correspond to the thickness of the outer bobbin 103. It istherefore possible to reduce variation in leakage inductance.Furthermore, a bobbin having a structure same as or similar to the outerbobbin 103 may be additionally arranged outside of the outer winding104. It is thereby possible to also improve the heat dissipatingproperty of the outer winding 104.

The transformer 101E may not have the core 107.

The T-shaped core 108 and the squared U-shaped core 109 are used in theexample depicted in FIG. 20, but there is no restriction thereto.

FIGS. 22 and 23 are perspective views schematically depicting otherexample configurations of the core. FIG. 22 depicts two cores 109 havinga squared U-shape when viewed from the X direction, and one core 110having an I-shape (i.e., a planar plate shape) when viewed from the Xdirection. As depicted in FIG. 23, two cores 110A, two cores 110B, andone core 110C having an I-shape (i.e., a planar plate shape) when viewedfrom the X direction may be used.

In the example depicted in FIG. 21, the winding axis of the innerwinding 106 and the winding axis of the outer winding 104 are shared,but there is no restriction thereto, and a central axis that isdifferent from the inner winding 106 and the outer winding 104 may beshared.

FIG. 24 is a cross-sectional view along an XY plane perpendicular to thewinding axis direction of a coil device 120 according to a modifiedexample of embodiment 5. The coil device 120 is provided with an innerbobbin 102, an inner winding 106, and a core 107. The inner bobbin 102includes a first bobbin member 102X and a second bobbin member 102Y. Theinner winding 106 is wound onto the inner bobbin 102 and the core 107 isarranged to thereby configure the coil device 120.

Due to the heat of the inner winding 106 being transmitted to the core107, the heat dissipating property can be improved even with the coildevice 120 in which, as in FIG. 24, an outer winding is not wound.Similarly, various coil devices can be designed by omitting the outerwinding from the transformers described in the various aforementionedembodiments. The present disclosure also includes such coil devices.

Embodiment 6

FIG. 25 is a circuit diagram depicting an example of a phase-shiftfull-bridge circuit 200. The phase-shift full-bridge circuit 200 of FIG.25 is widely used as a high-efficiency power source circuit in variousswitching power sources, and chargers such as an on-board charger, andpower converters, for example. The phase-shift full-bridge circuit 200is an example of a power conversion device.

The phase-shift full-bridge circuit 200 of FIG. 25 is provided with apair of connection terminals 211 and 212 that are connected to anexternal direct-current power source, four transistors 202, atransformer 101, a rectification circuit 204, a smoothing inductance209, and a smoothing capacitor 205. The phase-shift full-bridge circuit200 is further provided with a resonance inductance 207 and a resonancecapacitance 208. The full-bridge circuit, which is made up of the fourtransistors 202, is an example of a power conversion circuit. Therectification circuit 204 is an example of a power conversion circuit.

The four transistors 202 are connected to a primary winding of thetransformer 101. The four transistors 202 have the same configuration.The transistors 202 are metal-oxide film semiconductor field effecttransistors (MOSFETs) or insulated-gate bipolar transistors (IGBTs), forexample. The transistors 202 are formed of gallium nitride (GaN) orsilicon carbide (SiC), for example.

The four transistors 202 are turned on and off alternately such that thetop-right and bottom-left transistors 202 are off while the top-left andbottom-right transistors 202 are on, and the top-right and bottom-lefttransistors 202 are on while the top-left and bottom-right transistors202 are off, for example. Due to this switching, an alternating-currentvoltage is obtained from a direct-current voltage 201 that is input tothe pair of connection terminals 211 and 212. This alternating-currentvoltage is input to the primary winding of the transformer 101, and avoltage corresponding to the ratio of the number of turns of thetransformer 101 is generated in a secondary winding of the transformer101. This generated voltage is rectified by the rectification circuit204 and smoothed by the smoothing inductance 209 and the smoothingcapacitor 205, and a direct-current voltage 206 is thereby output.

In the phase-shift full-bridge circuit 200 of FIG. 25, in order tosuppress switching loss of the transistors 202, a zero volt switching(ZVS) technique implemented by a resonance circuit of the resonanceinductance 207 and the resonance capacitance 208 is used, for example.

For example, in the case where the transformer 101 according toembodiment 1 is adopted as the transformer 101 according to the presentembodiment, one from among the inner winding 106 and the outer winding104 may serve as the primary winding and the other may serve as thesecondary winding. Furthermore, in the phase-shift full-bridge circuit200 of the FIG. 25, any of the transformers 101A to 101E may be usedinstead of the transformer 101.

The phase-shift full-bridge circuit 200 of FIG. 25 is a power sourcecircuit for a comparatively large amount of power, and therefore a largeamount of heat is also generated from the windings of the transformerand a core. Thus, the heat dissipating property can be improved by usingthe transformers 101 and 101A to 101E. Furthermore, the weight of thecircuit can be reduced in the case where the resin molding is omitted orreduced in the transformers 101 and 101A to 101E.

It should be noted that a transformer or a coil device described in thevarious embodiments may be used for any of a resonance inductance, atransformer, and a smoothing inductance, and the same effect can bethereby obtained.

With regard to the power conversion device according to the presentembodiment, the example of the phase-shift full-bridge circuit 200depicted in FIG. 25 has been described, but there is no restrictionthereto.

FIG. 26 depicts an example of an LLC resonant half-bridge circuit 300.The LLC resonant half-bridge circuit 300 is an example of a powerconversion device. For example, the transformer 101 according toembodiment 1 may be adopted as the transformer 101 according to thepresent embodiment.

A transformer or a coil device described in the various embodiments maybe used in an LLC resonant full-bridge circuit for the power conversiondevice of the present disclosure. Alternatively, a coil device describedin the various embodiments may be used in a magnetic device such asreactor or a choke coil.

It should be noted that, in FIGS. 25 and 26, the resonance inductance207 may be realized by leakage inductance generated by leakage flux thatinterlinks with only one of the inner winding 106 and the outer winding104, and may be realized by external inductance. In the case where theresonance inductance 207 is realized with leakage inductance, externalinductance is not required, and therefore the size of the circuit can bereduced.

A magnetic device according to the present disclosure or a powerconversion device using the magnetic device can be applied in variouspower source circuits for consumer appliances to on-board chargers, forexample.

What is claimed is:
 1. A magnetic device comprising: a winding; andinsulators by which the winding is surrounded, each of the insulatorsbeing in contact with the winding, a gap existing between each twoadjacent of the insulators in a winding direction of the winding.
 2. Themagnetic device according to claim 1, wherein the insulators include afirst insulator and a second insulator.
 3. The magnetic device accordingto claim 2, wherein the insulators further include a third insulator. 4.The magnetic device according to claim 1, wherein the winding includes apair of linear portions that extend in a linear direction when viewedfrom a winding axis direction of the winding, a length of each of thepair of linear portions is longer than ¼ of a length of one turn of thewinding, and two of the insulators are in contact with the winding alongthe linear direction.
 5. The magnetic device according to claim 2,wherein the winding includes a first portion that extends in a firstdirection when viewed from a winding axis direction of the winding, anda second portion that extends in a second direction and is shorter thanthe first portion, and the gap between one end of the first insulatorand one end of the second insulator is located beside the secondportion.
 6. The magnetic device according to claim 2, wherein thewinding has a corner when viewed from a winding axis direction of thewinding, and the gap between one end of the first insulator and one endof the second insulator is located beside the corner.
 7. The magneticdevice according to claim 2, wherein one end of the first insulator andone end of the second insulator oppose each other through the gap, andthe one end of the first insulator and the one end of the secondinsulator each have a stepped end face.
 8. The magnetic device accordingto claim 2, wherein one end of the first insulator and one end of thesecond insulator oppose each other through the gap, the one end of thefirst insulator has a recess, and the one end of the second insulatorhas a protrusion that engages with the recess of the first insulator. 9.The magnetic device according to claim 1, further comprising: anotherwinding outside of the winding, the insulators being bobbins aroundwhich the other winding is wound.
 10. The magnetic device according toclaim 1, wherein the gap is larger than 0 mm and equal to or less than 3mm.
 11. A power conversion device comprising: the magnetic deviceaccording to claim 1; and a power conversion circuit that is connectedto the winding.